Radiation via tunneling from a de Sitter cosmological horizon

Hawking radiation can usefully be viewed as a semiclassical tunneling process that originates at the black hole horizon. The same basic premise should apply to de Sitter background radiation, with the cosmological horizon of de Sitter space now playing the featured role. In fact, a recent work (M. K. Parikh, hep-th/0204107) has gone a long way to verifying the validity of this de Sitter--tunneling picture. In the current paper, we extend these prior considerations to arbitrary-dimensional de Sitter space, as well as Schwarzschild--de Sitter spacetimes. It is shown that the tunneling formalism naturally censors against any black hole with a mass in excess of the Nariai value, thus enforcing a ``third law'' of Schwarzschild--de Sitter thermodynamics. We also provide commentary on the dS/conformal field theory correspondence in the context of this tunneling framework.